Sustainable intensification of corn through legume intercropping in Western Colorado
A field research initiative to reduce nitrogen fertilizer dependence in irrigated Mountain West corn production by intercropping with nitrogen-fixing legumes such as sun hemp, forage soybean, and cowpeas. The project evaluates optimal planting dates, soil health impacts, and economic viability to support sustainable intensification and scaling for local growers.
Overview
Irrigated corn growers in the Mountain West region typically apply high rates of nitrogen fertilizer because local soils are low in organic matter and nitrate. This leads to significant nitrogen losses through denitrification and leaching, creating environmental and economic challenges. This research program investigates whether intercropping corn with nitrogen-fixing legumes can reduce fertilizer requirements and improve soil health without sacrificing corn productivity. The work targets three objectives: determining optimal planting dates for corn paired with sun hemp, forage soybean, and cowpeas; assessing each intercropping system's impact on soil health and nitrogen cycling; and evaluating economic viability for growers in semi-arid Western Colorado.
Technical specifications
Cropping systems evaluated:
- Monoculture corn as the control treatment
- Monoculture legume plots for sun hemp, forage soybean, and cowpea
- Twin-row legume intercrops with a central corn row, with legumes separated by 44 cm
Experimental design:
- Split-plot field trial with four replicates at the Western Colorado Research Center
- Plot dimensions of six corn rows wide by thirty feet long
- Planting intervals of either a two-week or three-week gap between legume and corn planting to identify optimal timing
Key measurements:
- Grain and biomass yield across all treatments
- Soil nitrogen availability and nitrogen cycling metrics during corn anthesis
- Soil health and nitrogen status assessed again before the following year's corn planting
Legume performance basis:
- Forage cowpeas and forage soybean produced 4.2 to 6.3 t/ha dry biomass at 90 days after germination in prior variety trials
- Soybean can fix up to 103 kg N/ha and cowpeas up to 60 kg N/ha
- Legumes support distinct root microbiomes that can improve soil aggregation and carbon stabilization
Technology readiness level
The project is at an advanced field-validation stage. Prior variety screening in 2023 confirmed that forage cowpeas and forage soybean are high-biomass performers in the region. A local farmer in Loma, Colorado, has already evaluated sun hemp and corn intercropping, with preliminary observations showing marginal corn yield increases under certain planting configurations. Co-PI expertise includes cowpea evaluation under water-limited dryland conditions in eastern Colorado, including drought tolerance and varietal water-use variation. The next phase will generate quantitative data on nitrogen cycling, soil health, and economics to determine which intercropping systems are ready for grower adoption and scaling across the Mountain West.
About Colorado State University
Colorado State University is a comprehensive public land‑grant research university with an applied, partnership‑driven culture. Multiple research campuses—including the Fort Collins main campus, a public‑facing Denver site, and a foothills research complex with shared core facilities and pilot‑scale testbeds—enable companies to co‑locate, access instrumentation, and run validation studies. A statewide Extension network and proximity to the Front Range innovation corridor provide streamlined engagement with regional and national industry, while an integrated veterinary teaching hospital supports translational studies. Research is supported by competitive federal funding from agencies such as NSF, NIH, USDA, DOE, and DoD. A dedicated technology transfer office streamlines IP, contracting, and startup formation, with incubator and collaboration space for industry partners.
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